What Is Penetration Testing and How Does It Work?

Penetration testing, also known as pen testing or ethical hacking, is the practice of testing a computer system, network, or web application to find security vulnerabilities that an attacker could exploit. The goal of penetration testing is to identify weaknesses before malicious hackers can find and abuse them.

What is Penetration Testing?

Penetration testing involves mimicking the techniques and actions of real attackers to exploit vulnerabilities in a system. The tests are performed in a controlled manner with the permission of the organization.

The objective is to evaluate the security of a system by safely attempting to breach its defenses. This allows organizations to identify and address vulnerabilities before they are discovered and exploited by malicious actors.

Why Perform Penetration Testing?

There are several important reasons organizations utilize penetration testing:

Identify security vulnerabilities – Pen tests proactively uncover weaknesses in networks, systems, and applications that can be addressed before criminals exploit them. This allows organizations to improve their security posture.
Meet compliance requirements – Certain regulatory standards like PCI DSS require regular penetration testing. Pen tests provide evidence of compliance with infosec regulations.
Strengthen defenses – By understanding how vulnerabilities can be leveraged by attackers, organizations can better defend against real-world threats. Penetration testing allows security teams to improve their skills.
Validate security controls – Running penetration tests can verify that existing security controls like firewalls, IDS/IPS, and web application firewalls (WAFs) are correctly implemented and effective.
Prioritize remediation efforts – Reports from penetration tests help organizations focus their efforts on fixing the most critical security flaws first based on severity and potential impact.

Pen Testing vs Vulnerability Assessments

Penetration testing differs from vulnerability scanning, which simply identifies security flaws in an automated manner but does not actually exploit them. Vulnerability assessments are useful, but have limitations compared to simulations of real hacking techniques performed during penetration tests.

Key differences between pen testing and vulnerability assessments:

Goals – Pen tests focus on finding critical risks that could lead to system compromise. Vulnerability scans find all potential weaknesses but don‘t indicate severity/priority.
Techniques – Pen tests involve actively exploiting flaws using real hacking techniques. Vulnerability scans only detect weaknesses based on scans and audits.
Results – Pen test reports demonstrate the business risk and potential impacts of vulnerabilities. Vulnerability scan reports only list technical flaws.
Skills – Pen tests are performed by ethical hackers using their technical skills. Vulnerability scans rely on automated scan tools.
Limitations – Automated vulnerability scans have false positives and negatives. Pen tests validate vulnerability scan findings.
Perspective – Pen tests provide the attacker‘s perspective, helping identify risks that may be overlooked during vulnerability assessments.

Penetration Testing Methodology

Penetration testing typically follows a standardized methodology including these phases:

Planning – Define scope, rules of engagement, and schedule. Get written permission from management.
Reconnaissance – Gather information about the target environment through open source intelligence (OSINT), social engineering, and enumeration of systems/networks.
Scanning – Scan for vulnerabilities using automated tools to map out the attack surface.
Gaining Access – Attempt to gain entry to systems by exploiting vulnerabilities found during scanning. Employ techniques like SQL injection, password cracking, and social engineering.
Maintaining Access – Once inside, install backdoors, rootkits, or additional user accounts allowing persistent access even if original hole is patched.
Analysis – Document all vulnerabilities successfully exploited and review results to outline business risks.
Reporting – Deliver detailed report to client with findings, strategies to remediate, and recommendations to improve security.
Cleanup – Remove all backdoors, user accounts, footprints that were created during the penetration test. Restore systems to original state.

How Does Penetration Testing Work?

Penetration testing involves hands-on hacking techniques performed in a systematic process to compromise systems and evaluate security vulnerabilities.

Reconnaissance

Reconnaissance refers to gathering information about the target systems and infrastructure. The goal is to find out as much as possible about the environment in order to plan attacks effectively.

Penetration testers use a variety of manual and automated reconnaissance techniques such as:

Searching WHOIS, DNS records, and registrar databases
Mining organization websites, social media, and job postings
Identifying IP address ranges and domain names
Performing network scans to map out infrastructure
Enumerating server banners to determine operating systems and versions

Information obtained during the reconnaissance phase allows testers to identify promising avenues of attack.

Scanning

After gathering data on the target environment, the next step is to scan for potential vulnerabilities. Scanning involves using automated tools to probe systems, applications, and networks to uncover security flaws like misconfigurations, missing patches, weak passwords, and exploitable software bugs.

Common scanning techniques include:

Network scanning – Mapping open ports and services running on target systems using Nmap, Masscan, etc.
Vulnerability scanning – Detecting known software flaws using vulnerability scanners such as Nessus, OpenVAS, and Qualys.
Web application scanning – Crawling sites for security misconfigurations, XSS flaws, SQL injection issues using Burp Suite, Acunetix, etc.
Password cracking – Attempting to obtain password hashes and crack them using tools like John the Ripper and Hashcat.

The vulnerability scan results help penetration testers identify promising weaknesses to be exploited in the next testing phase.

Gaining Access

Armed with information from scanning, testers now attempt to exploit vulnerabilities to gain access to systems and data. Commonly employed techniques include:

SQL injection – Exploiting SQL flaws to steal data from databases.
Cross-site scripting (XSS) – Injecting malicious JavaScript into web apps to hijack user sessions.
Password attacks – Cracking weak passwords using brute force and dictionary attacks.
Privilege escalation – Upgrading from normal user access to administrator/root privileges by exploiting flaws.
Using malware – Deploying trojans, keyloggers, and remote access tools to gain persistent backdoor access.
Denial of Service (DoS) – Flooding sites and servers with traffic to crash and disrupt them.

The goal is to penetrate deep into the network environment and determine the extent of access an attacker could achieve.

Maintaining Access

Once inside the target systems, penetration testers will attempt to maintain their foothold so they can return later even if a vulnerability is patched.

Persistence techniques involve:

Installing software backdoors and rootkits able to survive OS reinstalls.
Creating additional privileged user accounts that remain after the test.
Modifying sensitive data while inside the network.
Capturing and exfiltrating data such as password hashes, source code, and databases.

Documenting the ability to maintain long-term access demonstrates significant risk from advanced persistent threats.

Analysis

Throughout the engagement, penetration testers take extremely detailed notes on vulnerabilities discovered and how they gained access.

During analysis, this evidence is correlated to:

Demonstrate potential business impacts – e.g. financial fraud, data breaches, service outages.
Identify which vulnerabilities pose the greatest risks.
Uncover weaknesses in existing defenses and security controls.
Pinpoint security gaps in workflows, network design, system configurations, and software coding practices.

Thorough analysis provides clients actionable insights on improving security based on real-world attack simulations.

Reporting and Remediation

The most important part of a penetration test is the final report detailing discoveries and how to remediate vulnerabilities.

Penetration Testing Report

Professional pentest reports include:

Executive summary for management highlighting biggest risks.
Detailed findings for each vulnerability exploited, including screenshots and proof of concepts.
Descriptions of business impact for each finding to demonstrate risk.
CVSS risk score, difficulty level, and remediation effort estimates for each vulnerability.
Recommended mitigation strategies and security best practices tailored to client‘s environment.

Well-written reports provide evidence of security gaps while clearly communicating risks and solutions to technical and leadership audiences.

Remediating Flaws

Armed with pen test results, organizations can:

Prioritize patching the most dangerous vulnerabilities enabling critical access first.
Improve processes around system hardening, access controls, patching, and configuration management.
Upgrade or reconfigure defensive tools like WAFs and IPS that failed to detect attacks.
Provide additional security training to staff based on social engineering success.
Implement stronger password policies and multifactor authentication based on password cracking results.
Architect more secure network designs, database schemas, and application code guided by lessons learned.
Allocate security resources to capabilities needing improvement based on testing weaknesses found.

Regular penetration testing and remediation helps maximize return on investment in cyber defenses.

Pen Testing Tools

Penetration testers leverage a vast toolkit of software to identify vulnerabilities and simulate real-world attacks:

Nmap – Powerful network discovery and port scanning utility.
Burp Suite – Web app testing platform useful for probing sites, capturing data, fuzzing, and content manipulation.
John The Ripper – Leading open source password cracking tool to obtain plaintext passwords from hashes.
sqlmap – Automates the process of detecting and exploiting SQL injection flaws to takeover databases.
Metasploit – Exploitation and payload framework very popular for developing custom pen testing scripts and tools.
Hashcat – Password recovery tool capable of brute forcing hashes at very high speeds using GPU processing power.
Wireshark – Network protocol analyzer useful for intercepting and inspecting traffic for sensitive data and other insights.
Hydra – Rapid online password cracking tool that performs parallel attacks against remote login pages.
Nessus – Commercial vulnerability scanner that detects thousands of common software flaws with minimal false positives.
Nikto – Open source web server scanner that searches for vulnerabilities like file uploads, outdated software, and poor encryption.

These represent just a small sample of the many feature-rich tools available to professional pen testers.

Benefits of Pen Testing for Businesses

There are many advantages to hiring professional penetration testers to assess your security:

Cost savings – It is much less expensive to invest in pen testing compared to recovering from cyberattacks and data breaches.
Risk reduction – Proactively finding and fixing security holes reduces your attack surface and risk to threats.
Regulatory compliance – Many regulations and standards mandate regular penetration testing. Demonstrate compliance to auditors.
Improved defenses – Pen tests enhance visibility into vulnerabilities while capturing attacker perspectives missed by internal teams. Security staff gain valuable experience.
Consumer confidence – Promoting pen testing provides confidence to customers that you take security seriously, helping build trust in your brand.
Competitive advantage – Strong cybersecurity translates into a competitive edge over other companies suffering breaches.

Penetration testing provides the most realistic assessment of your organization‘s ability to withstand real-world attacks. The insights gained allow smart investments in security and risk reduction.

Conclusion

Penetration testing is the practice of testing computer systems, networks, and applications to find and fix security vulnerabilities before malicious hackers exploit them. It involves simulated attacks against an environment to uncover risks before criminals compromise your systems and data.

Penetration tests provide insight from an attacker‘s point of view that organizations can use to strengthen their defenses. The methodology includes reconnaissance, vulnerability scanning, gaining access through exploits, maintaining persistence, analysis of capabilities demonstrated, detailed reporting, and remediation.

Regular penetration testing helps organizations identify critical security gaps, meet compliance mandates, and make strategic improvements to IT defenses. Implementing an ongoing pen testing program is one of the best investments an organization can make to reduce cyber risk and prevent breaches.